For many people, “plastic” is a one-word analog for environmental disaster. It is made from precious petroleum, after all, and once discarded in landfills and oceans, it takes centuries to degrade.

Then came apparent salvation: “bioplastics,” durable substances made from renewable cellulose, a plant-based polysaccharide. But problems remained. For one, the current bioplastics do not fully degrade in the environment. For another, their use is now limited to packaging material or simple containers for food and drink.